The invention relates to oil scraper piston ring assemblies mounted in grooves of pistons forming part of internal combustion engines. The oil scraper piston ring assembly comprises an oil scraper ring engaging that side wall of a piston groove which is closer to the combutsion chamber than the other side wall of the groove and a spring ring which extends essentially axially adjacent the oil scraper ring on that side of the latter which is oriented away from the combustion chamber. The spring ring is provided with alternating radial cuts to form resilient tongues and has a radially inner circular part situated radially inwardly of the oil scraper ring. The radially inner circular part is arranged obliquely with respect to a radially outer circular part of the spring ring, situated axially adjacent the oil scraper ring.
German Offenlegungsschrift (application published without examination) No. 2,023,850 discloses a two-part oil scraper piston ring assembly comprising an oil scraper ring and a spring. The oil scraper ring is formed of a cross-sectionally rectangular metal body which has a substantial dimension in the axial direction. The spring is formed of an angularly bent steel strip provided with alternating cuts. By means of axial force components of the spring, the oil scraper ring is pressed against one of the groove side walls while, at the same time, the spring is in engagement with the oppositely lying groove side wall.
German Pat. No. 1,232,419 discloses a multi-part piston ring assembly for insertion into a piston groove. The spring ring disclosed therein has, along its radially outer circumference, tongues bent in a direction away from the combustion chamber. The tongues are in contact with the outer circumference of a lower piston ring oriented towards the groove bottom. The spring ring is twisted in its unstressed state. At bent portions along the inner circumference of the spring ring there is provided a further piston ring which slidingly cooperates with the wall of the cylinder in which the piston reciprocates.
It has been a long-standing desideratum of the automotive industry to reduce mechanical power dissipation (losses), for example, by means of reducing the axial length of the piston. The axial dimension of the piston ring land may be conceivably reduced by reducing the total axial height of the oil scraper ring. Such a reduction of the axial dimensions, while preserving superior sealing properties may, however, not be realized either by means of three-part (relatively small-height) assemblies or by means of two-part assemblies having components of relatively large axial dimensions.